Prior to the upper sheet being welded together with the lower sheet, the package or the evacuating chamber receiving the package is evacuated so that the goods are not yet quite cooking at the packaging temperature. For example, goods which are suited for being deep-frozen are packaged in a hot condition. A packaging temperature of above 80.degree. C. is best because a sterilization of the goods is achieved at the same time. Further, a packaging of the goods is accomplished in such a manner that the space which remains within the package above the goods is without air. This is necessary because the oxygen contained in the air would oxidize the air and, because of the air entrapped in the package, would expand in a water bath during the usual warming up of the sealed package and would possibly burst the package.
For evacuating the air from the package it is known to close the package in an evacuating chamber.
However, the vacuum in the evacuating chamber cannot be chosen of any low degree, as already mentioned. The achievable vacuum depends on the type of the goods which must be packaged and on the temperature at which the goods are packaged. Thus, a residue of air remains in the package. To remove the air which remains in the package, it is known to blow into the evacuating chamber or directly into the package a steam or a gas and to subsequently close the package by putting the upper sheet and the lower sheet together.
In order to remove the air from the package through the vacuum chamber, either the upper sheet is made more narrow than the lower sheet, so that the latter cannot be gripped by the two sides of the upper chamber half, or the lower and/or upper sheets have perforations therein.
The steam which is blown into the package removes the air from said package. After the assembly, for example by welding the upper sheet and lower part of the package together, there will be exclusively a steam or a gas in the free space above the goods. During venting of the evacuating chamber and after cooling off of the goods, the steam condenses, so that an air-empty space is created above the goods. Since the entire vacuum chamber including the package must be filled with gas or steam, a high usage of gas is the result.
The basis purpose of the invention is to construct the packaging device described above in such a manner that the evacuation and blowing in of steam into the package can be carried out substantially quicker than with the known devices and the packaging device is less expensive to manufacture.
This purpose is attained inventively by a packaging device, which is characterized by at least one half of the evacuating chamber having on at least one side of its edge engaging the opposite half a recess, into which recess is snugly received a nozzle bar which is connected to a steam supply line. This inventive device permits a considerable savings in gas, because only the package itself needs to be filled with gas. According to a preferred embodiment of the invention one nozzle bar each is mounted on two oppositely positioned sides of the evacuating chamber.
Through this arrangement one obtains a quick and thorough flushing of the package, in particular if the package is evacuated by a nozzle bar which is connected to an evacuating pipe, while steam is blown into the package through the other nozzle bar.
The nozzle bar of the invention can be mounted on each side of the packaging device with the exception of the sheet outlet side. If the nozzle bar is mounted on the sheet inlet side, then it is possible if the upper sheet is narrower than the upper half of the evacuating chamber, to evacuate the package through the upper half of the evacuating chamber, while through the nozzle bar exclusively steam is blown into the package. If an upper sheet is used, which is wider than the evacuating chamber, then the package must be evacuated through the nozzle bar and must subsequently be steamed or gassed.
In an arrangement of the nozzle bar in the area of the sheet edges, the upper sheet is arranged at this point so that it is engaged by the frame of the upper half of the evacuating chamber. The nozzle bar grips then between the upper sheet and the lower sheet, so that the steam can be introduced directly into the package. If the upper sheet is also engaged on the other side by the upper half of the frame of the evacuating chamber, then the evacuation of the package is done also through the nozzle bar. Also in the case of an evacuation of the package through the nozzle bar, both halves of the evacuating chamber are evacuated, because otherwise the sheets of the package are pressed together prior to the welding through the air pressure resting on them and thus, for example, liquid goods can escape. On the other hand, evacuation of the package itself would be more difficult.
According to a further embodiment of the invention, the nozzle bar is resiliently suspended so that during a driving together of the upper and lower chamber halves a tight seal between the nozzle bar and the two chamber halves is obtained. At least in the upper half of the evacuating chamber there are arranged in the area of the nozzle bar sealing elements. These sealing elements in connection with the resilient support of the nozzle bar effect an absolutely tight seal of the evacuating chamber and of upper and lower sheets of the package from the outside air.